As long as the send/receive button remains in first position (default) in the Quick Access Toolbar (top left), you can also press Alt+1 to manually send all and check for new emails.

To change how often Outlook checks for new emails, click on "File" (top left) and choose "Options": select "Advanced" on the left and scroll down to "Send and Receive".

When sending emails with Outlook closed, those stay in the outbox: with "Send immediately when connected" checked (default), Outlook automatically sends message in the outbox.

Click the "Send/Receive" button to see by default only one "Send-receive group" ("All Accounts") - the first checkbox makes sense if you've separated accounts into groups.

If you uncheck "Schedule an automatic send/receive every [5] minutes", you'll need to remember to manually check for new messages and send anything in your outbox; optionally increase/decrease the default number of minutes between automatically sending/receiving.

Check "Perform an automatic send/receive when exiting" to force Outlook to send emails in your outbox and check the mail server for new ones just before it closes.

Under "When Outlook is Offline", pressing F9 or clicking "Send/Receive" will still work unless you uncheck the "Include this group in send/receive (F9)" checkbox.

Likewise, Outlook won't send or receive emails when offline, unless you check "Schedule an automatic send/receive every..." (and optionally include a different number of minutes).

Click "Close", and then click "OK" in Options, to return to your emails.